Heart valve disease is a widespread condition in which one or more of the valves of the heart fails to function properly. Various surgical techniques may be used to replace or repair a diseased or damaged valve. In just one way, in a valve replacement surgery, damaged leaflets of the valve are excised and the annulus is sculpted to receive a replacement valve. Another less drastic method for treating defective valves is repair or reconstruction, by annuloplasty, in which the effective size of the valve annulus is contracted and reinforced, by attaching a prosthetic annuloplasty repair segment or ring to an interior wall of the heart around the valve annulus. The annuloplasty ring is designed to support the functional changes that occur during the cardiac cycle; maintaining coaptation and valve integrity.
One of the two atrio-ventricular valves in the heart is the tricuspid valve. The tricuspid valve regulates blood flow between the right atrium and the right ventricle. Anatomically speaking, the tricuspid valve 10, as seen in FIG. 1, includes an annulus 12 that is the portion of the wall of the heart where three valve leaflets 14, 16, 18 (septal, anterior, and posterior, respectively) insert into the heart wall tissue. The leaflets 14, 16, 18 extend inward into the valve or flow orifice defined by the annulus 12. There are three commissures between the three leaflets, which include an anteroseptal commissure 20, a posteroseptal commissure 22 and an anteroposterior commissure 24. Chordae tendinae 26 connect the leaflets to papillary muscles located in the right ventricle to control the movement of the leaflets. The tricuspid annulus 12 is an ovoid-shaped structure ring at the base of the valve. The annulus 12 has contractile function and can change shape throughout a cardiac cycle. The portions of the tricuspid valve annulus 12 that are attached to the septal 14, anterior 16 and posterior 18 leaflets are called the septal 34, anterior 36 and posterior 38 aspects, respectively. The anterior and posterior leaflets are also known, respectively, as the anterosuperior and inferior leaflets. Similarly, the aspects of the annulus may be referred to using these alternative terms.
With particular regard to the tricuspid valve, the primary dysfunction is dilation of the anterior and posterior aspects of the valve annulus. Annulus dilation can lead to incomplete leaflet coaptation, causing a condition known as tricuspid regurgitation. Studies have shown that the posterior aspect can be dilated as much as 80% of its original length, whereas the anterior aspect can be dilated by as much as 40% (Carpentier et al. (1974), Surgical management of acquired tricuspid valve disease, Journal of the Thoracic Cardiovascular Surgeon 67(1): 53-65). The septal aspect of the annulus lies along the atrioventricular septum of the heart and does not dilate as much as the other aspects (typically 10% or less of its original length).
Consequently, when a tricuspid valve is repaired surgically, the goal is to reduce the size of and reinforce one or both of the anterior and posterior aspects of the valve annulus. Early methods used to reduce the size of the anterior and/or posterior aspects were suture-based. One method called “bicuspidization” used sutures to effectively eliminate the posterior leaflet, and is described in Sharony et al. (2003), Repair of Tricuspid Regurgitation: The Posterior Annuloplasty Technique, Operative Techniques in Thoracic and Cardiovascular Surgery, November; 8(4) 177-183. Another method called “sliding plasty” involves separation of the leaflets from the annulus, plication/shortening of the annulus, and reattachments of the leaflets, and is described in Minale et al. (1987), New Developments for Reconstruction of the Tricuspid Valve, J. Thorac. Cardiovasc. Surg., October; 94(4): 626-31. Yet another method used, called the “modified DeVega tricuspid annuloplasty,” involves placing a suture or series of sutures around the annulus and pulling the sutures tight to reduce the perimeter of the annulus, as described in Antunes et al. (2003), DeVega Annuloplasty of the Tricuspid Valve, Operative Techniques in Thoracic and Cardiovascular Surgery, November; 8(4): 169-176.
One current method used to reduce the tricuspid valve annulus is remodeling annuloplasty. Remodeling annuloplasty involves implanting a prosthetic ring or band in a supra annular position. The purpose of the ring or band is to restrict and/or support an annulus to correct and/or prevent valvular insufficiency. Remodeling annuloplasty is an important part of surgical valve repair. Three objectives of surgical valve repair include: 1) restore large surface of leaflet coaptation; 2) preserve leaflet mobility; and 3) stabilize the annulus and avoid further dilatation. In remodeling annuloplasty, both annuloplasty rings and annuloplasty bands are used for repair of valves. In general terms, annuloplasty rings completely encompass a valve annulus, while annuloplasty bands are designed to primarily encompass only a portion of the valve annulus. Examples of annuloplasty bands are shown in U.S. Pat. Nos. 5,824,066, and 6,786,924, and PCT International Patent Publication No. WO00/74603, the teachings of which are incorporated herein by reference.
Annuloplasty surgery associated with the tricuspid valve is generally intended to restore normal leaflet coaptation by reversing annulus dilation through plication. A way to restore leaflet coaptation is to restore the annulus to its normal or native shape during ventricular contraction or systole. However, the shape of the tricuspid annulus during portions of the cardiac cycle has not been well defined. Recent publications provide evidence that the tricuspid valve annulus has a nonplanar or 3D structure, which is described as “saddle-shaped,” and undergoes complex geometric changes during the cardiac cycle. (See, Fukuda et al. (2006), Three Dimensional Geometry of the Tricuspid Annulus in Healthy Subjects and in Patients with Functional Tricuspid Regurgitation: A Real-Time, 3-Dimensional Echocardiographic Study, Circulation, 114: 492-498; Ton-Nu et al. (2006), Geometric Determinants of Functional Tricuspid Regurgitation: Insights From 3-Dimensional Echocardiography, Circulation, 114: 143-149; Hiro et al. (2004), Sonometric Study of the Normal Tricuspid Valve Annulus in Sheep, The Journal of Heart Valve Disease, 13(1): 452-460).
In close proximity to the tricuspid valve is the atrioventricular (AV) node 28 (FIG. 1). The AV node is a section of nodal tissue that delays cardiac impulses from the sinoatrial node to allow the atria to contract and empty their contents and also relays cardiac impulses to the atrioventricular bundle. In order to maintain AV node function, during annuloplasty surgery, a surgeon generally attempts to avoid suturing in or near the AV node. Annuloplasty bands, or C-rings, are, therefore, good choices for use, in repair of the tricuspid valve. The annuloplasty bands include a break or opening that may be generally positioned in the area including the AV node in order to avoid the need for suturing in that area. However, since the AV node is not visible to the surgeon, there is the possibility that while securing the endpoints of the annuloplasty band, sutures may be placed in tissue including the AV node.
The AV node is situated in the lower atrial septum at the apex of a triangle known as the Triangle of Koch (TOK), which is an area of heart tissue framed or bounded by certain anatomical landmarks in the heart. Two sides of the TOK are formed by the tendon of Todaro and the septal aspect of the tricuspid annulus. The base is marked at one end by the coronary sinus orifice and the other end by the septal annulus. The region known as the TOK has been the focus of research relating to the cure of supraventricular arrhythmias that arise near the AV node. Additionally, surgical and catheter ablation techniques have made use of the TOK as an anatomic landmark for ablation.
Despite multiple annuloplasty methods and devices currently on the market, there is a continued desire to improve such methods and devices. Particularly, there is a desire to have devices and methods that better accommodate the anatomy of the heart and the shape of the heart throughout the cardiac cycle, and thereby improve results associated with valve repair surgery.